Inductive coupling



Dec. 23, 1947. BRADDQN ET AL 2,432,982

INDUCTIVE COUPLING Filed NOV. 11, 1942 "I I v/ m 645 54 FIG INVENTORS F. D. BRADDON L.J. DE LANTY B O..E L 4 M ii gouzv Patented Dec. 23, 1947 INDUCTIVE COUPLING Frederick D. Braddon,

Lanty, Baldwin,

Babylon, Loren J. De and Orland E. Esval, Huntington, N. Y., assignors to Sperry Gyroscope Company, Inc., New York Brooklyn, N. Y., a corporation of Application November 11, 1942, Serial No. 465,284

4 Claims.

This invention relates generally to an improved type of inductive coupling or transformer which is particularly adapted, by virtueof the novel features thereof, for use in gyroscopic structures and for use with Selsyn-type transmitters, receivers or signal transformers, particularly when employed in magnetic compass systems.

functions when energized to exert an upward thrust on its bearing shaft which, when coupled withor mounted on that of the Selsyn, serves to relieve the weight of the rotor on the bearings and thereby reduce friction.

- With the foregoing and other objects in view, our invention includes the novel elements and the combinations and arrangements thereof described below and illustrated in the accompanying drawings, in which- Fig. 1 is a sectional elevation view of one form of our inductive coupling associated with a Selsyn-type transmitter or receiver, forming a unit adapted for use in magnetic compass systems;

Fig. 2 is a plan view partially in section of the device shown in Fig. 1, taken in about the plane 2-2 thereof;

Fig. 3 is a detail view of one of the permeable discs employed in the form of transformer construction illustrated in Fig. 1;

Fig. 4 is a fragmentary elevation view, partially in section, showing the use of another form of inductive coupling or transformer with parts of a gyroscopic instrument;

Fig. 5 is a somewhat view, partially in section, the type of transformer illustrated in Fig. 4; and

Fig. 6 is a view similar to Fig. 4, but showing a modified form of inductive coupling.

As above indicated, the inductive couplingor transformer of the present invention is particularly adapted for use with a Selsyn-like transenlarged, perspective of one of the cores of or inductive coupling mitter, receiver or signal transformer where such instruments are employed in magnetic compass systems or the like. The reason is because in systems of this character, it is very desirable to reduce theload on those parts of the system, such as the magnetic compass itself, which are incapable of exerting any great amount of torque. The inductive coupling reduces friction losses because it eliminates slip rings and brushes and the like which, of course, increase the friction of the instrument. Furthermore, in one form of the present invention, the inductive coupling functions to exert an axial thrust on the shaft of its rotor which may be common with the rotor of the-Selsyn, so that, when the axis of rotationof the Selsyn lies in a vertical direction, as it commonly does when employed as a pickoif in a magnetic compass system, it may function to. exert an upward thrust on the Selsyn rotor, thereby serving additionally to decrease the friction in its bearings. Hence, in the following, we have described the preferred forms of inductive coupling or transformer of our invention in connection respectively with those parts of instruments or devices with which they are particularly adapted for use. Referring to Figs. 1, 2 and 3, in accordance with a preferred embodiment of our invention, a Selsyn-type transmitter and one form of our novel transformer are incorporated within a unitary housing 45 which is generally cylindrical in form. Housing 45 is fixedly mounted and shaft ii of the repeating means or transmitter is rotatably mounted in relation to the same by means of bearings 46 and 41. When used in compass systems, shaft [5 is vertically situated and its angular position maybe determined by a suitable follower magnet (not shown). The stator winding 33 of the illustrated Selsyn-type instrument is secured within the housing as shown and the single phase rotor winding 28 is suitably mounted on the rotor core on the shaft l5. The construction shown for the Selsyn-type instrument, per se, is conventional. Binding posts 48, 4'9 and 50 are situated on the housing 45 for leads (not shown), the same being connected to the three phase stator windings 33. Energy is supplied to rotor winding of the Selsyn-type transmitter, in this instance, by means of our improved transformer or inductive coupling, the same eliminating the use of the customary brushes in this connection.

The shown inductive coupling is situated between relatively fixed and rotatable members, respectively, the housing 45 and the shaft is in this instance. Energy is fed from a suitable alternating current source to the binding posts 5| and 52 on the housing 45. Electrical leads or suitable conductors connect the binding posts 5| and 52 with the stationary winding 53 of the transformer. In the present instance, winding 53 is the primary winding of the inductive coupling. In the embodiment illustrated, winding or coil 53 is wound on a non-conducting ring 54' and is inserted within an annular magnetically permeable core or ring 54 that is fixedly mounted on an external flange 58 within the housing 45. The secondary winding, in this instance, of the transformer is indicated at 51, the same being situated on a magnetically permeable spool shaped core 58. Core 58 is mounted on and fastened to rotate with shaft l5. The output of winding 51 is fed to the rotor of the Selsyn instrument by suitable connecting leads 58 and 80 which are secured to the shaft by an insulating sleeve 8|. The respective windings of the transformer are arranged in concentric relation and the cores defining the magnetic circuit of the coupling are similarly arranged. In the form of coupling shown in Fig. l, the magnetic circuit also includes end discs 62, Fig. 3, which are situated at the respective ends of the annular core 54. Discs 82 may be radially slotted as shown at 83 to prevent eddy current losses. The core 54 and discs 62 are held within the housing 45 in spring pressed relation by means of a strong spring 64. A cross section of this portion of the magnetic circuit is U-shaped, the fixed arms of the U extending in axially spaced relation to the respective ends of the circular spool shaped rotor core 58. The rims of spool 58 are preferably constructed to include radial slots. The air gaps when considered in terms of the least distance between the relatively fixed and rotatable cores in this instance lie in an axial direction with respect to the axis of rotation of the rotatable member or shaft l5. Radial play in the bearings l6 and 41 is consequently not effective to change the reluctance in the magnetic circuit and consequently alter the output of the transformer from the output desired. Instead of the, ring and double disc arrangement shown, this construction may comprise a ring having one Of the discs formed as an integral portion thereof so that the ring may be considered to have a flange at one end. The single disc in this construction is utilized at the open end of the flanged ring. It is apparent that the Selsyn instrument described may be used as a brushless receiver in which event, the primary and secondary windings of the transformer function in reverse relation and the output of the Selsyn rotor is taken from binding posts 5i and 52.

In the combination Selsyn instrument and transformer shown in Fig. l, the air gap between the top of spool 58 and disc 62 is designed to be smaller than the gap between the bottom of the spool 58 and its related disc 82. The difference in reluctance in portions of the magnetic circuit because of this arrangement causes an upwardly directed thrust to be exerted along shaft Hi. This thrust is of a sufficient magnitude to substantially counterbalance the load on the bearings of the instrument due to the weight of the vertical shaft and the parts thereon.

In the form of the invention shown in Figs. 4 and 5, a modification of the inductive coupling described is shown, in'which the relatively fixed and rotatable members are respectively a gimbal ring 55 and a rotor bearing case 85 of a gyroscopic instrument. Trunnion 61 of the case 88 may be normally situated in a horizontal plane in this instance, such as provided in the journal pivot structure of the rotor bearing case in the vertical ring of a conventional directional gyro instrument. The fixed magnetic spool of the coupling shown in Fig. 5 is mounted in the vertical ring between a spacer ring 88 and an end plate 69. This spool as indicated at 10 is of an inverted type whose slotted rims H and 12 are of different diameters. The spool is arranged within a receiving base in the vertical ring in concentric relation to the axis of trunnion 81. The winding for core 10 is indicated at 13. In this form of the invention movable core 14 is fixedly mounted on the trunnion 51. Core I4 is spool shaped and includes radially slotted rims of different diameters as respectively indicated at 15 and 15. Further, the respective cores 10 and 14 are arranged with the relatively small and large rim areas oppositely disposed so that the two spacings or gaps in the magnetic circuit are along the axis of the trunnion. The winding for spool 14 is indicated at 11.

With reference to Fig. 6, a coupling arrangement for supplying three phase alternating current energy to a motor adapted to spin the gyro rotor within the rotor bearing case of a 'gyro instrument is shown to include a group of three axially spaced or insulated couplings, respectively indicated at 18, 19 and 88. These units are similarly constructed and include a movable spool shaped wound core 8| fixed to trunnion 81 and an inverted spool shaped wound core 82 secured to the fixed member or ring 65 and encircling the core 8|. Core 82 is concentrically positioned with relation to movable core 8|. The spaced rims of the respective cores are disposed in adjacent relation to complete the individual magnetic circuits through each of the couplings 18, I8 and 80. Each of the spool shaped cores employed in the various forms of the invention shown includes a number of radially extending air gap providing slots similar to the showing thereof made in Fig. 3. The couplings are spaced from one another by means of suitable insulation.

As many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. An inductive coupling between relatively fixed and rotatable members comprising a permeable cylindrical core fixedly mounted in coaxial relation on the rotatable member, a winding for said cylindrical core, an annular permeable core secured to the fixed member and encircling the cylindrical core and arranged in concentric relation thereto, a winding for said annular core, and two permeable discs contacting respectively the opposite ends of the annular core and extending radially in side by side and in close axially spaced relation to opposite ends of the cylindrical core, said cylindrical core, annular core and discs being comprised in a mag netic circuit.

2. An inductive coupling between relatively fixed and rotatable members comprising a" permeable cylindrical core fixedly mounted in coaxial relation on the rotatable member, awinding for said cylindrical core, a permeable ring secured to the fixed member partially surrounding the cylindrical core and arranged in concentric relation thereto, said ring having a flange at one end thereof, a winding for said ring, and a permeable disc contacting the other end of the ring and extending radially in side by side and in close axially spaced relation to one end of the cylindrical core, the flanged end of the ring extending radially in side by side and in close axially spaced relation to the other end of the cylindrical core, said cylindrical core, flanged ring, and disc being comprised in a magnetic circuit.

3. An inductive coupling comprising an inner, cylindrical core and an outer core supported in concentric relation for relative rotation about an axis coincident with the axis of said cylindrical core, windings on each core, and two permeable discs respectively contiguous opposite ends of the outer core and extending radially in side by side and in close axially spaced relation respectively to opposite ends of the inner core, said inner and outer cores and discs being comprised in a magnetic circuit.

4. An inductive coupling comprising inner and outer cores supported in bearings for relative rotation about a. vertical axis, windings on each core, said cores each having end portions at opposite ends of each respectively extending radially in side by side and in close axially spaced relation to form air gaps therebetween, the upper air gap being of lesser axial length than the lower whereby to provide an axial thrust to decrease the load on said bearings when in operation.

FREDERICK D. BRADDON. LOREN J. DE LANTY. ORLAND E. ESVAL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

